Shu read where a frequent traveler made it a point to learn 40 words from each country that he visits. So, I wonder...what 40 words would you choose?

I think "beer" would definitely be on my list and on the lists of several other wordcrafters I suspect.

Bathroom...or loo...or rest room...or toilet...or whatever, would be on mine.

Also, "how much is?", which would count as 1 word.

No country I want to visit doesn't have "beer" in its native language, whether native or loan word.
And, having consumed your fill, you would want to ask for directions to the W.C. So, I guess those two words just about have it covered. So what are the other 38 for? Airport? Again almost universal. Taxi? Universal.

If you ask "How much is..." you'd need to know what the reply meant, so best not to ask, just pay up!

It's always good to learn some phatic expressions, such as: "hello", "good morning", "thank you", "you're welcome", etc. After that some common words for food and drink. Then some standard ways of asking "where is X?" (for store, restaurant, hotel, WC, police station, etc. Count to 10. It's probably more than 40 words, but who says it has to be forty?

Good point, z. One would be better served by knowing useful phrases rather than individual words. One would no doubt be thought crazy for standing in the middle of a street in Madrid and shouting, "baño." Prefix it with "Donde es el" and you'll be much better off. Well, you'll still be thought crazy for standing in the street and shouting it, but at least the locals will understand that you're a loco tourist who has to pee. Thus do I submit that it's better to know twenty phrases than forty words.

One thing I learned when I was in Sicily with a number or Europeans is how easy it is to communicate without knowing the language. Mind you, I wasn't good at it, but my Danish friends were excellent.

I would need to learn the word for "library".

I think "bibliothèque" or a variation thereof would work in Europe when "library" didn't. It would work in Spanish and German as well as French, so that's an easy one, IMHO.

And I think "sick" or something similar would be necessary.